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An investigation has been launched into the Christmas Day death of a U.S. citizen who became unresponsive while in custody in a holding cell at the Campo Border Patrol station near San Diego.

According to information released Saturday by U.S. Border Patrol officials, the man was arrested Christmas Eve at a border checkpoint on Interstate 8 after Border Patrol agents allegedly discovered drug paraphernalia and trace amounts of methamphetamine inside the man’s vehicle.

San Diego Sector Border Patrol officials said the man was arrested by agents for illegal possession of drugs and intent to distribute three pounds of marijuana. He was then taken to a holding cell at the Campo Border Patrol station.

Later that evening, while in the holding cell, the man became incoherent and unresponsive, according to Border Patrol officials. Border Patrol emergency medics administered CPR to the man and called paramedics.

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However, when paramedics took over, they were unable to revive the man and he was pronounced dead shortly after midnight on Christmas Day, officials said.

No further details were released by Border Patrol officials about what may have led to the man’s sudden death while in custody.

An investigation has been launched and the San Diego County Medical Examiner’s office will ultimately determine the man’s cause of death.

The Department of Homeland Security Office of Investigator General (OIG) is also investigating the incident.

For their part, San Diego Sector Border Patrol said it’s “cooperating fully with these investigators to ensure a neutral third party reviews all evidence and information surrounding this unfortunate death.”

Officials have not released the name of the man.

However, according to Alliance San Diego, a community group that promotes social justice, the man is 58-year-old Steven Keith. A San Diego news outlet reports Keith was en route to Ocean Beach for a Christmas visit at the time of his arrest and death.

On Saturday, Andrea Guerrero, executive director of Alliance San Diego, told NBC 7 that Keith’s death while in Border Patrol custody is disturbing, and the group will seek full transparency in the case.

“We are deeply concerned that yet another person has died in Border Patrol custody, this time a US citizen. The public and the family deserve a full accounting of what happened,” said Guerrero.

“Border Patrol has an unfortunate history of abuse and neglect of people it detains, and the agency operates without any known custody standards, such as the police have. Because of this, on Dec. 12th, Senator Boxer introduced a bill, S.B. 1817, the Humane Short Term Custody Act, to set minimum detention condition standards to prevent abuse and neglect. Unfortunately, this may have come too late for Mr. Keith. Alliance San Diego and our allies along the border will monitor this case along with more than 20 other deaths that have happened since 2010,” she added.